This research is directed towards elucidation of the functions of phosphorylated proteins and the associated protein phosphorylation and dephosphorylation reactions in the cell nucleus. The current phase of the work is concentrated on the study of lysine-rich histone phosphorylation and histone phosphorylating enzymes which occur specifically in growing cells, and on the relationship between hormone- regulated histone phosphorylation and the control of RNA synthesis. The properties of the enzymes, the sites of phosphorylation in the histone, and the effect of phosphorylation at various sites on the interaction of the histone with DNA will be examined. The preferential phosphorylation of one or more sites in lysine-rich histone in response to various conditions such as hormone administration or rapid cell division is also under study, in hopes of determining the role of the various types of histone phosphorylation in cell replication, growth and genetic regulation.